Electric double layer: Particles dispersed in a liquid medium may become charged in one of two main ways. Ionic species present in a solution may be adsorbed at the surface or, alternatively, charges on the surface may arise due to […]
The term ‘rheology’ was derived from the Greek words rheo (flow) and logos (science) and is used to describe the flow of liquids and the deformation of solids. Viscosity is an expression of the resistance of a fluid to flow: […]
Thixotropy: Thixotropy is defined as the progressive decrease in viscosity with time for a constant applied shear stress followed by a gradual recovery when the stress is removed. Thixotropy is a time-dependent shear thinning property. Thixotropy can be defined as […]
STABILITY OF COLLOIDAL SYSTEMS: Colloidal particles undergo frequent collisions as a result of Brownian motion. Whether these collisions result in coagulation (permanent contact or close aggregation of particle), flocculation (temporary contact or large aggregates) or whether the particles rebound and […]
A disperse system is defined as a heterogeneous two-phase system in which the disperse phase is distributed as particles or droplets throughout another phase called as dispersion medium. Based on the size of dispersed particles within the dispersion medium, the […]
PROPERTIES OF COLLOIDAL DISPERSIONS: Kinetic Properties: Brownian motion- Brownian motion describes the random zigzag movement of colloidal particles. Colloidal particles are subject to random collisions with the molecules of the dispersion medium; hence, each particle pursues an irregular and a […]
PHARMACEUTICAL BUFFERS: Buffers are used to establish and maintain ion activity within narrow limits. The most common buffered systems in pharmacy are used: To establish hydrogen-ion activity for the calibration of pH meters. To prepare isotonic dosage form formulations. To […]
Buffers are substances or a combination of substances that, by their presence in solution, resist changes in pH upon the addition of small quantities of acid or alkali. Buffered solutions are necessary in many experiments conducted in pharmaceutical research. Drug […]